The day may come when the rest of the animal creation may acquire
those rights which never could have been witholden from them but by the
hand of tyranny. The French have already discovered that the blackness
of the skin is no reason why a human being should be abandoned without
redress to the caprice of a tormentor. It may one day come to be recognized
that the number of legs, the villosity of the skin, or the termination
of the os sacrum are reasons equally insufficient for abandoning
a sensitive being to the same fate. What else is it that should trace the
insuperable line? Is it the faculty of reason, or perhaps the faculty of
discourse? But a full-grown horse or dog is beyond comparison a more rational,
as well as a more conversable animal, than an infant of a day or a week
or even a month old. But suppose it were otherwise, what would it avail?
The question is not, Can they reason? nor Can they talk?
but, Can they suffer?

--Jeremy Bentham

If a being suffers, there can be no moral justification for refusing
to take that suffering into accountÖ If a being is not capable of suffering,
Ö, there is nothing to be taken into account.

--Peter Singer

We describe bat sonar as a form of three-dimensional forward perception;
we believe that bats feel some versions of pain, fear, hunger, and lust,
and that they have other, more familiar types of perception besides sonar.
But we believe that these experiences also have in each case a specific
subjective character, which it is beyond our ability to conceive.

--Thomas Nagel

I. Introduction

The topic of this paper lies within the densely structured but largely
unexplored region of overlap between the philosophy of mind and normative
ethics. For convenience, I call this region the ethics of mind.
What I want to discuss in this paper, in particular, is the moral significance
of the phenomenal consciousness or subjective experience of different types
of animals, and in particular the comparative moral significance of the
subjective experience of pain across different types of animals.

II. The Mental-Mental Gap and its Consequences

Everyone knows that Thomas Nagelís famous essay "What is it like to
be a bat?" is all about gaps in the philosophy of mind. It is now commonplace
to distinguish carefully between an explanatory gap, and an ontological
gap. An explanatory gap obtains just in case one set of concepts cannot
be reduced to another set of concepts, whether by analytical definition,
or by some weaker kind of reduction such as necessary coextension. By contrast,
an ontological gap obtains just in case one set of properties or facts
cannot be reduced to another set of properties or facts, whether by identity,
or by some weaker kind of reduction such as necessary equivalence or logical
(strong) supervenience. An explanatory gap is consistent with, but does
not automatically entail, the existence of an ontological gap. That is,
one can defend nonreduction for some pair of (sets of) concepts, but still
assert reduction for the corresponding pair of (sets of) properties picked
out by those concepts. So it is possible to defend the existence of an
explanatory gap in the philosophy of mind while denying the existence of
an ontological gap. It is also possible to assert the existence of an explanatory
gap, and remain agnostic about the existence of an ontological gap. And
although this option was not so obvious when "What is it like to be a bat?"
first appeared, it is now clear that this is Nagelís thesis. What very
few seem to have noticed, however, is that he actually discloses two
explanatory gaps in the philosophy of mind, and not just one.

First and foremost, there is Nagelís well-known explanatory gap between
mentalistic concepts and physicalistic concepts. Mentalistic concepts are
concepts whose content and ascription imply phenomenal consciousness, subjective
experience, or the first-person point of view: in Nagelís terms, what
it is like to be for an organism. Physicalistic concepts by contrast
are concepts whose content and ascription imply only first- or second-order
physical properties or facts, the objective character of the natural world,
or the third-person/impersonal point of view: what it is for something
to be fundamentally physical. Nagelís claim here is that physicalistic
or third-person/impersonal concepts can never adequately explain the subjective
character of conscious experience. Let us call this "the mental-physical
gap."

But second, for Nagel there is also a seemingly equally intractable
explanatory gap between the mentalistic concepts that we apply to animals
such as ourselves, and the mentalistic concepts that we apply to the conscious
states of other kinds of animals. Nagelís claim here is that we are incapable
of understanding the specifically subjective character of the conscious
experience of other species. As he puts it in another essay:

We ascribe experiences to animals on the basis of their behavior,
structure, and circumstances, but we are not just ascribing to them behavior,
structure, and circumstances. So what are we saying? The same kind of thing
we say of people when we say they have experiences, of course. But here
the special relation between first- and third-person ascription is not
available as an indication of the subjectivity of the mental. We are left
with concepts that are anchored in their application to humans, and that
apply to other creatures by a natural extension from the behavioral and
contextual criteria that operate in ordinary human cases. This seems definitely
unsatisfactory, because the experiences of other creatures are certainly
independent of the reach of an analogy with the human case. They have their
own reality and their own subjectivity.
Let us call this "the mental-mental gap."

Those closely familiar with the structure of "What is it like to be
a bat?" will notice that I have reversed Nagelís order of argumentation.
He initially discusses the mental-mental gap, and then consequently
discusses the mental-physical gap. Officially then, the mental-mental gap
is supposed to be the basic premise in the argument for the mental-physical
gap:

This [mental-mental gap] bears directly on the mind-body problem.
For if the facts about experience--facts about what it is like for the
experiencing organism--are accessible from only one point of view, then
it is a mystery how the true character of experiences could be revealed
in the physical operation of that organism.
In other words, for Nagel the mental-mental gap is supposed to entail the
mental-physical gap. Now I do not know whether I am the only one who has
ever felt a little queasy about this step in Nagelís argument. But in any
case it has always seemed to me that although the mental-mental gap is
perfectly consistent with the mental-physical gap, nevertheless
the two gaps are in fact logically independent of one another.

On the one hand, it is possible to hold that we cannot understand the
specifically subjective character of the conscious experience of other
animal species and also that reductive materialism is true, so that
there is no mental-physical gap. It is true that at least one version of
reductive materialism--a hyper-strong version of the type-type mind-brain
identity theory that implies both the analytically or logically necessary
identity of mentalistic concepts with physicalistic concepts, and also
the metaphysically necessary identity of mental properties with physical
properties--is sufficient for closing the mental-mental gap: therefore
closing the mental-mental gap is necessary for this version of reductive
materialism. But since not every version of reductive materialism is of
this hyper-strong sort, and since most reductive materialists, including
the defenders of classical "type-physicalism," have in fact also explicitly
rejected the hyper-strong type-type mind-brain identity theory,it
seems obvious that closing the mental-mental gap is not generally necessary
for the truth of reductive materialism. Nor, indeed, is closing the mental-mental
gap generally necessary for materialism of any sort.

On the other hand and conversely, even if there is a mental-physical
gap, it does not necessarily follow that there is a mental-mental gap.
Assume the existence of the mental-physical gap. Then assume the truth
of some non-Cartesian version of dualism to the effect that some or even
most nonhuman animals have immaterial souls that are fundamentally the
same as ours. Then further suppose that one fine day, like Dr Dolittle,
we somehow learn to "talk to the animals" and are thereby able to read
the conscious minds of other species. Or far less implausibly, again assuming
the existence of an explanatory gap between mentalistic concepts and physicalistic
concepts but this time rejecting dualism, suppose that by some completely
non-magical means--say, via the imaginative simulation of non-human animal
embodiment, guided by empathy and cognitive ethology (i.e., the scientific
study of animal minds and especially non-human animal minds in the context
of macro-biology, cognitive psychology, and behavioral psychology)--we
come to understand the specifically subjective character of the conscious
mental states of some or even most non-humans with the same reliability
and conceptual anchorage as our understanding of the subjective character
of the conscious mental states of other humans. So there can be a mental-physical
gap but no mental-mental gap.

For these reasons, Nagelís mental-mental gap is logically independent
of his mental-physical gap. From this point forward, I am going to assume
that the mental-mental gap is logically independent of the mental-physical
gap, and also that Nagelís argument for the existence of a mental-mental
gap is fundamentally sound. The main purpose of this paper is to argue
that if there is a mental-mental gap, then we have good reason to
believe not only (i) that the pain of human or non-human animals that are
persons is more morally significant than the pain of any animals of any
species that are non-persons, but also (ii) that the pain of any animals
of any species that will become persons in the natural course of
their genetic development is more morally significant than the pain of
any animals of any species that will never become persons in the
natural course of their genetic development. This two-part thesis is what
I call the moral comparison principle or the MCP.

If true, the MCP entails we have good reason to believe that the pain
of normal humans at any point in the natural course of their genetic development
past the achievement of sentience, the pain of other suitably emotionally
complex but abnormal humans (including many victims of Alzheimerís disease,
autism, cerebral palsy, Downís syndrome, and spina bifida), and the pain
of normal apes at any point in the natural course of their genetic development
past the achievement of sentience, are all more morally significant than
the pain of any bats, cats, dogs, horses, cows, etc., and also more
morally significant than the pain of any seriously brain-damaged and merely
sentient humans. The overall view of moral status implied by the MCP is
what I call "the person-oriented conception."

It should be already obvious that for me, the crucial moral difference
between different kinds of animal minds is not the difference between
human minds and non-human minds. Rather for me the crucial moral difference
is between (1) animals that have merely a capacity for phenomenal consciousness,
and (2) animals that in addition to possessing a capacity for phenomenal
consciousness, are also persons in the moral sense. Now it is obvious,
I think, that every actual or possible animal capable of fully understanding--even
if disagreeing with!--this essay is a person in the moral sense, by virtue
of possessing psychological capacities for logical reasoning, practical
decision-making, recognizing and attributing moral obligations, and reflective
self-consciousness. But for reasons I will discuss in section IV, I want
to hold that some pre-linguistic humans, some partially linguistic humans,
and some partially linguistic or non-linguistic non-human animals are also
persons, by virtue of possessing a psychological capacity for the momentary
(but not necessarily long term) and self-conscious (but not necessarily
reflective) evaluation of their own (but not necessarily othersí) affective
states, together with a capacity for intentional animal agency. So I reject
speciesism. Speciesism says that some or another species-specific difference
between animals is the sole or primary determinant of the moral significance
of those animals or moral discriminations between those animals. Speciesism
is false and wrong, just as racism and sexism are false and wrong. But
just because speciesism is false and wrong, it does not follow that every
species-specific difference between animals is wholly irrelevant to the
determination of moral significance or moral discriminations. On the contrary,
Nagelís mental-mental gap entails that at least some species-specific differences
between animals play a necessary role in the determination of the moral
significance of animals and moral discriminations between animals.

As we will see in section V, perhaps surprisingly, two of the basic
reasons for taking the MCP to be true, along with Nagelís mental-mental
gap, are (1) Hilary Putnamís "multiple realization thesis," and (2) Jaegwon
Kimís "structure-restricted correlation thesis." But perhaps even more
surprisingly, as I will argue in section III, the fourth basic reason for
accepting the MCP is a sharp distinction between pain and suffering, which
carries along with it the notion of personhood, or the concept of a person
in the moral sense. So while Bentham and Singer are correct that an animalís
capacity for suffering is of fundamental moral significance, they are nevertheless
mistaken that every animal capable of experiencing pain is thereby
capable of suffering. All and only persons in the moral sense can suffer.
In particular then, I think that we have good reason to believe that bats
are capable of experiencing pain, but no good reason to believe that bats
are capable of suffering, precisely because bats are not persons in the
moral sense.

I anticipate that not only speciesists but also many animal ethicists
are not going to like my conclusions. Nevertheless in order to reject my
conclusions, dissenters are going to have to reject some very solid and
widely-accepted theses in mainstream contemporary philosophy of mind: the
mental-mental gap, the multiple realization thesis, and the structure-restricted
correlation thesis. As I mentioned, the other basic premise in my argument
is the sharp distinction between pain and suffering, and along with it,
a corresponding concept of a person in the moral sense. These are the topics
of the next two sections.

III. Pain and Suffering

I accept Nagelís canonical description of consciousness as what-it-is-like-to-be-for-an-organism.
This is the same as what contemporary philosophers of mind call Ďphenomenal
consciousnessí. Phenomenal consciousness, in turn, is the subjective
experience of an animal. Phenomenal consciousness is "subjective" because
it necessarily includes an ego or first person, and it is "experience"
because it necessarily includes embodied sensations, feelings, and affects,
particularly pleasure or pain, and more generally various mental states
of animals to the extent that they have specific intrinsic qualitative
or structural characters of sentience.

For the purposes of this paper, animals are sentient living organisms
that become and remain individual members of their species just insofar
as they possess a species-specific neurobiological causal basis of phenomenal
consciousness or subjective experience (see section IV). But it is important
to note that the notion of sentience is not precisely the same as
the notion of subjective experience. Sentience is the organismís capacity
for embodied sensation, feeling, and affect, particularly pleasure or pain.
More broadly speaking, one can think of sentience as "the feeling of life"
or "vital experience." All phenomenal consciousness necessarily includes
sentience as a fundamental component. But the available psychological,
neurobiological, and ethological evidence strongly suggests that Ďsentientí
is a vague predicate, and that sentience is to some extent a matter of
degree. Thus it seems very likely that not every species of living organism
which arguably has some appreciable degree of sentience--say, bees, sharks,
or snakes--actually has a subjectively centered or ego-based type
of sentience, that is, a subjective "point of view." What this means is
that the notion of a sentient living organism or animal, insofar as it
is studied by cognitive ethologists and philosophers of mind, generally
presupposes that the animal has passed some basic threshold of degrees
of overall psychological, neurobiological, and behavioral organization
into a definitely centered or ego-based form of sentience, that is, phenomenally
conscious sentience. But it must also be admitted that there are extended
uses of Ďsentient organismí that apply to borderline cases falling just
below this basic threshold (e.g., bees, sharks, or snakes), and thus that
the concept of sentience is not precisely the same concept as the concept
of phenomenal consciousness or subjective experience. Another more linguistic
way of putting this is to say that for me while Ďsentientí is a vague predicate,
Ďconsciousí is not a vague predicate because it applied to all and
only those sentient organisms that have passed a definite basic psychological,
neurobiological, and behavioral threshold into subjectivity or egocentricity.
But it is up to cognitive ethologists, not philosophers, to determine precisely
where that definite basic threshold lies.

As we have just seen, sentience is a living organismís capacity for
experience, that is, embodied sensation, feeling, and affect, particularly
pleasure or pain, whether this sort of experience is subjectively centered
(egocentric) or not. But in any case necessarily all phenomenally conscious
animals are sentient. So obviously phenomenal consciousness is closely
bound up with the capacity for experiencing pain.

Pain is the subjective experience of an animal in direct response to
tissue damage or neurobiological systemic disruption caused by various
intrusive exogenous stimuli such as burns, cuts, and collisions, or by
various noxious endogenous stimuli including relatively enduring conditions
such as disease or neurosis, and more temporary conditions such as migraine
or emotional distress. It is empirically known that in humans at least,
both the degree and also the specific character of pain are not wholly
determined by the amount of tissue damage or neurobiological systemic disruption
but in fact are partially determined by other factors such as anxiety-level,
attention, prior experience, and suggestion. This is what I call thesubject-dependency of pain. Moreover it is widely held by contemporary
philosophers of mind that the causal-functional characterization of pain--that
is, pain as characterized abstractly and relationally in terms of the overall
pattern of causal transitions from sensory and behavioral stimulus inputs
to the animal, through the specific neurobiological constitution of the
animal, to behavioral outputs from the animal--can be held fixed, while
systematically varying the specific neurobiological constitution of the
animal. This is what I call themultiple realizability of pain.
And it is also widely held by contemporary philosophers of mind that the
specific character of the subjective experience of pain can be held fixed,
while systematically varying the causal-functional characterization of
pain. This is what I call the multiple functionality of pain.

Pain needs to be distinguished from pain-behavior. Behavior in
general is how an animal moves or orients its body in response to exogenous
or endogenous stimuli. Pain-behavior in particular is the characteristic
set of unlearned or uncultivated species-specific behavioral responses
to tissue damage or neurobiological systemic disruption. It seems correct
to say that necessarily, other things being equal, if an animal is in pain,
then it will also exhibit the pain-behavior of its species. This in turn
implies that pain-behavior is, under some conditions, a reliable indicator
of pain. But pain is not strictly speaking identical to pain-behavior,
because when other things are not equal, it is possible for an animal or
indeed even an entire species of animals to be in pain but fail to exhibit
the pain-behavior of its species;and conversely, even when
other things are equal, it remains possible for all the members of that
species to fake pain by exhibiting the relevant pain-behavior without
actually being in pain.

This brings me to a crucial distinction between (1) bodily pain
and (2) suffering.

Bodily pain is pain that is phenomenally spatially localized in some
part or parts of the animalís body for a certain definite duration of time,
and also has a bodily cause. The actual bodily cause of bodily pain may
not be spatially localized in the same area that pain is phenomenally spatially
localized: this is vividly evident, for example, when pain is phenomenally
spatially localized in a phantom limb. Nevertheless, bodily pain is necessarily
always phenomenally spatially localized somewhere or another in the animalís
body or its body-image. All bodily pain has a bodily cause, in the sense
that some event inside or at the surface of the animalís body is a sufficient
condition, under some psychological-cum-neurobiological law (i.e., a law
that is "hedged" or ceteris paribus ), of a pain-event that is not
earlier than the first event. But given the subject-dependency of pain,
the degree of bodily pain may be altogether out of proportion to the actual
extent of tissue damage or neurobiological systemic disruption. Bodily
pain is also multiply realizable and multiply functional. It is possible
for both humans and bats to have the same causally-functionally characterized
type of bodily pain (e.g., by being burned or cut); and it is also possible
for the same subjective experience of bodily pain to have different causal-functional
characterizations and thereby play different causal-functional roles (e.g.,
the ordinary subjective experience of being burned or cut vs. masochism).

Suffering by contrast is the emotional pain of a person, which
may or may not also involve any bodily pain, hence need not necessarily
be spatially phenomenally localized (although suffering is always experienced
during a certain definite duration of time), and need not necessarily have
a bodily cause that is also the cause of bodily pain. Like bodily pain,
suffering is subject-dependent (the degree or specific character of suffering
is partially dependent on anxiety-level, attention, prior experience, and
suggestion), multiply realizable (martians can suffer too), and multiply
functional (the same subjective experience of suffering can play different
causal-functional roles--there are suffering masochists, just as there
are bodily pain masochists). Both bodily pain and suffering can be alleviated
by drugs: sometimes by the same drug (e.g., alcohol), although usually
by different ones (e.g., ibuprofen vs. anti-depressants). But suffering
cannot always be alleviated by drugs, whereas bodily pain always
can be. In persons, bodily pain can indeed constitute suffering,
which is to say that in persons there can be a spatiotemporal coincidence
between phenomenally localized pain and the cause of suffering. For example,
I can suffer when my left leg hurts and just because my left leg has been
damaged. But in principle, that token experience of suffering could have
been spatiotemporally coincident with another different phenomenally localized
bodily pain, and similarly with a different token of that type of suffering:
I might have identically suffered, whether it was my left leg or my right
leg that was hurting (token suffering can be preserved under phenomenal
enantiomorphism in the body); and I might have suffered in just the same
way, whether it was my leg or arm or head that was hurting (type suffering
can be preserved under change of phenomenal spatial localization in the
body).

This points up the crucial fact that bodily pain is not equivalent with
suffering, despite the obvious fact that bodily pain and suffering often
go together. It is possible to be in considerable bodily pain but not suffer
at all (e.g., high performance athletes, professional dancers, sadomasochistic
sex, Stoics, etc.), and it is also possible to suffer intensely but not
be in any sort of bodily pain (e.g., extreme embarrassment, extreme shyness,
guilt, jealousy, extreme disappointment, anxiety, fear, depression, and
as the result of certain forms of emotional trauma such as rejection, betrayal,
loss of a loved one, etc.). More generally, suffering essentially expresses
a self-conscious subjectís frustrated or despairing sense of the inner
or outer limits of his or her own intentional agency. I suffer because
I am not what I want to be or the way I want to be, or because the
world is not what I want it to be or the way I want it to be, or
because other people are similarly recalcitrant in relation to my desires
and my will. Our world is a vale of tears. But agent-centered frustration
or despair can occur without any bodily pain, and bodily pain can occur
without agent-centered frustration or despair.

It follows that pain does not always or necessarily involve suffering.
This fact in turn directly implies that Benthamís and Singerís famous implicit
inference from animal pain to animal suffering is fallacious: so for later
reference, I will call this "the Bentham-Singer Fallacy."

A crucial feature of suffering, as opposed to bodily pain, is that all
and onlypersons can suffer. This is because suffering requires
an emotional complexity that is characteristic of all and only persons.
Briefly put, all and only persons are capable of higher-order or self-conscious
volitional pain, or suffering--pain that essentially expresses a self-conscious
animalís frustrated or despairing sense of the inner or outer limits of
its own intentional agency--and a capacity for having higher-order or self-conscious
volitional states is at least a necessary condition of personhood and perhaps
also a sufficient condition of personhood. Now of course I need to say
more about the nature of a person in the moral sense. But before I do that
I must also say something about animals and individuals.

IV. Animals, Individuals, and Persons

On the view I wish to spell out and defend, necessarily all persons
are animals, but not all animals are persons. Furthermore, necessarily
every person is also an individual animal belonging to some species or
another, but not every particular member of that species is even an individual,
much less a person.

What is an animal? The Oxford English Dictionary tells us that the word
Ďanimalí means "a living organism which feeds on organic matter, usually
one with specialized sense organs and nervous system, and able to respond
rapidly to stimuli." In biology on the other hand, Ďanimalí has a more
technical meaning, in that animals constitute one of the five kingdoms
of living things: Monera (bacteria), Protoctists, Fungi, Plants, and Animals.
The class of animals in this biological sense includes both vertebrates
and invertebrates. My usage of Ďanimalí in this paper however is a precisification
of the ordinary language term and is intended to coincide with its use
in cognitive ethology.

Cognitive ethologists, by hypothesis, take the animals they are studying
to be organisms with various mental capacities, including sentience, phenomenal
consciousness, sense perception, imagination, desire, and volition. That
includes all or at least most vertebrates, and possibly some but probably
not all invertebrates. This may seem distressingly vague. But in fact the
boundaries of the class of animals as conceived in cognitive ethology cannot
now be precisely fixed. For example, are insects, fish, and reptiles animals
in this sense? No one really knows. No doubt, sooner or later the boundaries
will be more precisely fixed. Nevertheless, as I mentioned in the context
of my earlier discussion of the sentience vs. phenomenal consciousness
distinction, I regard such boundary-fixing as an empirical matter that
is up to cognitive ethologists, not philosophers of mind. So no matter
how cognitive ethology ultimately determines the boundary between animals
and mere living organisms, I can assent to it.

What I am primarily interested in is how cognitive ethologists characterize
those living organisms that now definitely fall into the class of
animals in their sense of Ďanimalí: for example, humans, monkeys, bats,
cats, horses, wolves, dogs, birds, bears, cows, mice, and so on. It is
of course not possible to summarize the empirical results of cognitive
ethology in a few words. But even at the risk of over-simplification, I
can nevertheless say with some confidence that animals in the cognitive
ethologistís sense are living organisms that (i) are token-reflexive foci
of a variety of causal and semantic (informational) transactions with their
local environments; (ii) are causal sources of a variety of self-initiated
and informationally-sensitive movements in space and time; (iii) are capable
of sense-perception, feeling, and affect, particularly pleasure and pain,
and therefore have a sentient life of some sort; and finally (iv) have
a "point of view," that is, have an egocentric, somatic (proprioceptive
and kinesthetic) perspective, which may, as in the case of primates (and
birds) be dominated by vision, but need not be, as in the case of echolocating
bats. Speaking generally and philosophically, then, I will say that animals,
as characterized by cognitive ethology, are sentient phenomenally conscious
active living organisms.

Animals are individual members of their species. But not every particular
living organism that belongs to a given species is an individual member
of that species. For example, a human zygote or embryo (the sperm-fertilized
ovum) is a particular living organism that belongs to the human species
in the purely biological sense of sharing our species-specific genetic
code: but a human embryo is not necessarily a human individual. This is
for three reasons. First, early human embryos up to about the 14th
day of their existence are "totipotential." This means, among other things,
that one embryo can split and become two distinct human individuals (twins),
and also that two embryos can fuse and become a single human individual
(chimeras). Second, conjoined twins (i.e., so-called "Siamese twins," or
humans with two distinct brains but only a single set of vital organs)
constitute a particular living human organism, but they are not the same
human individual. Third, anencephalic human babies (i.e., babies born with
a functioning brain stem but no cerebral hemispheres or higher brain functions)
are particular living human organisms, but not human individuals.

What then is an individual member of some species? My proposal is that
something X is an individual belonging to some species S
if and only if X is a particular living S-type organism and
X also possesses a neurobiological causal structure or organization
sufficient for the manifestation of a unique phenomenal consciousness or
subjective experience under determinate real-world conditions. It should
be noted that the uniqueness of subjective experience does not necessarily
imply a unified subjective experience, where a capacity for the
subjective unification of experience (i.e., "unity of consciousness" in
one sense of that phrase) is the subjectís capacity simultaneously to combine
all currently experienced qualitative characters or representational contents
within a single conscious phenomenal field. For example, I am capable of
divided conscious attention but nevertheless remain a unique consciousness
even if for some reason (say, blindsight, commissurotomy, or masking) it
is impossible for me to bring together all my currently experienced qualitative
characters or representational contents with a single conscious phenomenal
field. So according to my criterion of individuality, not only is each
conjoined twin a distinct individual, but also each commissurotomy patient
is a distinct individual. Or quite generally speaking: no matter what species
S you belong to, you are precisely or numerically the very same
S-type individual from the very moment you acquire the neurobiological
causal basis of your unique S-type consciousness, and you continue
to be precisely or numerically the very same S-type individual as
long as this neurobiological causal structure or organization continues
to exist, until the very moment this neurobiological causal basis is destroyed
or permanently disrupted, and you are never precisely or numerically the
same S-type individual otherwise. Or on other words, an individual
is not merely alive: it is the subject of a life. This implies,
for example, that the unfortunate Karen Quinlan was not the same human
individual before and after her catastrophic car accident, precisely because
after her accident the human individual that she had been in fact no longer
existed. Thus Karen Quinlanís life ended with her accident, although a
particular living human organism causally continuous with her body survived
the accident. Nor of course was Karen Quinlan the same person before and
after her accident, precisely because after her accident the person that
she had been also in fact no longer existed.

This brings me to the concept of a person in the moral sense. The basis
of my analysis is Harry Frankfurtís well-known and influential hierarchical
volitional theory of persons, according to which "one essential difference
between persons and other animals is to be found in the structure of a
personís will." Frankfurtís account begins with the notion of a desire.
A desire is a felt need (as opposed to an actual need: not all felt needs
are actual needs) for something, or a preference for something, or a wish
for something. To desire X is to want X; and to desire to
X is to want to X. According to Frankfurt, some animals have
not only "first-order desires," which are ordinary direct desires for things
or events, but also "effective first-order desires." Effective first-order
desires are desires that move (or will move, or would move) the animal
all the way to action. An effective first-order desire is the same as an
animalís will or first-order volition. First-order desires
may or may not be accompanied by "second-order desires": to want (not)
to want X, or to want (not) to want to X. If so, some of
the second-order desires may be directed to the determination of precisely
which first-order desire is the effective first-order desire, or the animalís
will and first-order volition; and such desires are "second-order volitions."
Whatever their order-level however, all desires or volitions can be either
conscious or non-conscious. For convenience however I will concentrate
exclusively on conscious desires and volitions.

According to Frankfurt all and only persons have second-order
volitions, because all and only persons care about the constitution of
their wills. By contrast to persons, creatures that are "wantons" have
effective first-order desires, but they either lack second-order desires
(hence they cannot care about the constitution of their wills) or if they
have second-order desires they nevertheless lack second-order volitions
(hence they can but in fact do not care about the constitution of their
wills). Again according to Frankfurt, all non-human animals, all human
infants, and some human adults are wantons. Finally, a person has freedom
of the will if and only if she can determine by means of a second-order
volition precisely which among her first-order desires is the effective
one. This is also known as "identification" or "decision"; otherwise persons
have unfreedom of the will. Wantons have neither freedom of the will nor
unfreedom of the will, simply because they are not persons.

I disagree with Frankfurtís hierarchical volitional theory of persons
on two relatively minor but still fairly significant points.

First, I doubt that Frankfurtís notion of personhood adequately captures
the broadly-speaking Kantian sense of personhood, according to which
persons are what I will call "higher-level" or "Kantian" rational animals,
that is, animals capable of norm-guided logical or practical reasoning,
moral self-legislation, and reflective self-consciousness. Higher-level
or Kantian rationality involves the possession of capacities for the recognition
of necessary truth, a priori belief or certainty, and non-instrumental,
altruistic, non-hedonistic, non-consequentialist obligation or the
"categorical Ďoughtí." By sharp contrast, what I will call "lower-level"
or "Humean" rationality involves only the possession of capacities for
the recognition of contingent truth, a posteriori belief, and instrumental,
self-interested, hedonistic, consequentialist obligation or the "hypothetical
Ďoughtí." All animals with a capacity for higher-level or Kantian rationality
also possess a capacity for lower-level or Humean rationality, but not
the converse. Toddlers and bonobo apes, for example, are Humean or lower-level
rational animals but not Kantian rational animals. Animals with a capacity
for rationality in the higher-level or Kantian sense are constrained in
their intentional agency by the Categorical Imperative or at least by some
other suitably universal, non-instrumental, altruistic, non-hedonistic,
and non-consequentialist moral principles. By contrast, animals with merely
a capacity for rationality in the lower-level or Humean sense are constrained
in their intentional agency only by (at least some of) the axioms of rational
choice theory.

Now some animals are persons in Frankfurtís sense, and also rational
in the lower-level or Humean sense, but not rational in the higher-level
or Kantian sense. Anyone who has looked after a toddler knows that it is
possible for an animal to care very deeply about the constitution of her
will but not (yet) be capable of norm-guided logical or practical reasoning,
moral self-legislation, or reflective self-consciousness. Again, a toddler
can identify or decide in the Frankfurtian sense by using a second-order
volition to determine precisely which among her first-order desires is
her effective first-order desire. But the identifications or decisions
of toddlers are at best momentary or temporary, and do not occur consistently
or over an extended period of time. As everyone knows, toddlers are fickle
and willful. In this way, toddlers are capable of many different sorts
of complex affects and complex emotional states, but they are not higher-level
or Kantian rational animals. So toddlers are persons in the Frankfurtian
or hierarchical volitional sense, but not persons in the Kantian sense.
This subtlety in the notion of personhood can be conceptually finessed
by distinguishing between K(antian)-persons and F(rankfurtian)-persons.
All K-person are F-persons, but only some F-persons
are K-persons.

The K-person vs.F-person distinction between can
be further elaborated by further unpacking the subtle differences between
K-persons and toddlers. As everyone knows, toddlers exemplify the
fact of phenomenal consciousness and are also minimally self-conscious
in the sense that they can recognize themselves in a mirror and make simple
judgments about some of their own mental states. They may also know a few
words of their native natural language. They have simple beliefs, and if
they do know a few words of their language, they can carry out some simple
inferences. They want things. Also they usually know what they want, and
they care a great deal about getting what they want. They can mentally
cause movements of their own bodies by means of their volitions. They know
their own names. They are intellectually curious, have capacious memories
and wonderful imaginations, and are sometimes highly insightful. But they
are also extremely naïve and uncritical, highly emotional, highly
inconsistent in their behavior, and above all fickle and willful,
and certainly cannot be held personally or morally responsible for their
actions. They are incapable of conceiving their own lives as a whole. They
cannot engage in retrospective or prospective self-interpretation and self-evaluation,
explicit step-by-step deliberation about immediate action, or long-term
planning. They do not know the normative significance of their own deaths--that
persons must strive to make their individual finite lives into meaningful
and coherent wholes. They need to be most carefully looked after, gently
but firmly told what to do, loved unconditionally, and at all times protected
from the vicissitudes of an often unfriendly and violent world. They are
not autonomous in the Kantian sense, or capable of moral self-legislation.
Otherwise put, toddlers are F-persons because they engage directly
in the process of constituting their wills by means of second-order volitions,
but they are not (yet) rational agents in the higher-level or Kantian sense
of rationality.

What then is the basic difference between K-persons or rational
animals in the higher-level or Kantian sense, and F-persons? The
answer is that K-persons or rational animals in the higher-level
or Kantian sense are inherently non-instrumental-reasons-giving or categorically
normative-reflective animals, while F-persons are not inherently
so. In other words, rational animals in the Kantian or higher-level sense
are inherently capable of giving non-instrumental reasons for their beliefs
and actions, and thus are inherently capable of being categorically normatively
self-guided in their beliefs and actions, whereas at least some F-persons
are not capable of this. Or in still other words, rational animals in the
Kantian or higher-level sense have a capacity for a priori epistemic and
practical justification and in particular for a priori epistemic and practical
self-justification, whereas at least some F-persons do not.

Second, I disagree with Frankfurt about the scope of the class of wantons.
In particular, in view of strong evidence from cognitive ethology, I believe
that at least some non-human animals--and in particular, apes--are F-persons.

These two minor critical extensions of Frankfurtís theory are of fundamental
moral importance. If I am correct that both K-persons and F-persons
are persons in the moral sense, then it follows that rationality in the
higher-level or Kantian sense is not a necessary condition of personhood
(although of course it remains a sufficient condition). On the contrary,
the necessary and sufficient condition of personhood is hierarchical volitional
emotional complexity, or the capacity for second-order volitions, whether
or not this is accompanied by a capacity for norm-guided logical or practical
reasoning, moral self-legislation, and reflective self-consciousness. This
directly implies the existence of a class of persons between mere animals
and higher-level or Kantian rational animals. And if, in turn, as many
philosophers and non-philosophers alike believe, an animal has a right-to-life
if and only if it is a person, this directly implies that it is the psychological
capacity for having complex emotional states and in particular second-order
volitions, that necessarily and sufficiently triggers a right-to-life,
not higher-level or Kantian rationality.

Closely related to the right to life is what I will call the right
not to suffer. The right not to suffer is the right not to be unjustly
caused to suffer. Its moral rationale is that since (other things being
equal) a personís permanent death is always a bad thing for that person,
and since the only morally sufficient reason for the moral permissibility
of euthanasia or mercy killing--whether voluntary or involuntary, or active
or passive--is the prevention of personal suffering, the only thing that
can be worse for a person than to die or to be killed is to be caused to
suffer. So if there is a right not to be unjustly killed (i.e., the right
to life), then there must also be a right not to be unjustly caused to
suffer. In this way, just as the psychological capacity for having complex
emotional states and in particular second-order volitions necessarily and
sufficiently triggers a right-to-life, so too it necessarily and sufficiently
triggers the right not to suffer.

Now I believe that all toddlers, as well as some abnormal humans, including
many victims of Alzheimerís disease, autism, cerebral palsy, Downís syndrome,
and spina bifida, are F-persons but not K-persons. If I am
right about this, then it follows that all toddlers and many victims of
Alzheimerís disease, autism, cerebral palsy, Downís syndrome, and spina
bifida have a right-to-life and also a right not to suffer by virtue of
their hierarchical volitional emotional complexity, despite their being
incapable of norm-guided logical or practical reasoning, moral self-legislation,
and reflective self-consciousness, not to mention their also being pre-linguistic
animals or partially linguistic animals. Furthermore, if I am also correct
that not all non-humans are wantons, and that there are some non-human
F-persons (e.g., apes), then it also is directly implied by this
fact together with the above points that some non-humans have a right-to-life
and also a right not to suffer by virtue of their hierarchical volitional
emotional complexity, despite their being incapable of norm-guided logical
or practical reasoning, moral self-legislation, and reflective self-consciousness,
not to mention their also being partially linguistic or non-linguistic
animals. Or more bluntly put, I am saying that morally we should care every
bit as much about apes (and possibly other primates, as well as whales
and dolphins) as we already do about toddlers and about many victims of
Alzheimerís disease, autism, cerebral palsy, Downís syndrome, and spina
bifida. But time and energy spent morally worrying about normal human fetuses
prior to the onset of sentience or phenomenal consciousness, or about bats,
cats, dogs, horses, cows, etc., or about humans that are merely and permanently
sentient, in persistent vegetative states, or anencephalic, are probably
wasted time and energy. Now I want to try to prove this explicitly.

V. The Moral Comparison Principle

My argument for the Moral Comparison Principle or the MCP, as I mentioned
in section II, uses four basic premises: (1) the mental-mental gap; (2)
the sharp distinction between pain and suffering, along with the corresponding
concept of a person in the moral sense; (3) the multiple realization thesis;
and (4) the structure-restricted correlation thesis. I have already explicated
(1) and (2). So before we get to my argument for the MCP proper, I need
to say something about (3) and (4).

Both the multiple realization thesis and the structure-restricted correlation
thesis arise out of philosophical debates about functionalism. Functionalism
holds that mental properties are not intrinsic or necessary and non-relational
properties of something, but are instead functional properties:
extrinsic or contingent and relational properties of something. More precisely,
functional properties are patterns of occurrent or dispositional causal
transitions from inputs to outputs, applying to the external and internal
states of physical machines or living organisms. Standard examples of functional
properties are the properties instantiated by sequences of digital computations
in a Turing machine, and the properties instantiated by those neurobiological
processes in the brains and central nervous systems of animals that are
apt to cause behavior. According to materialist functionalism, functional
properties are second-order physical properties that are supervenient on
first-order physical properties: so the materialist functionalist holds
that mental properties are identical to a certain special sort of second-order
physical property.

Materialist functionalism is committed to the truth of both the multiple
realization thesis and the structure-restricted correlation thesis. The
multiple realization thesis asserts that one and the same functional property
can be instantiated in many different actual or possible physical individuals,
types of organism, natural kinds, and compositional stuffs. This is verified
by the fact that the very same computational software can be instantiated
in many different sorts of hardware, and that the very same type of neurobiological
process (e.g., digestion) can be instantiated in many different species
of animals (e.g., humans and cats). The structure-restricted correlation
thesis, on the other hand, asserts the relativization of the instantiation
of mental properties to species-specific or even sub-species-specific physical
structure types, or as Kim puts it:

If anything has mental property M at time t, there is
some physical structure type T and physical property P such
that it is a system of type T at t and has P at t,
and it holds as a matter of law that all systems of type T have
M at a time just in case they have P at a time.
In other words, mental properties occur in animals under specific physical
conditions in a lawful way, and this lawful regularity is found across
whole species or sub-specific groups sharing the same physical constitution.
If mental properties are functional properties, then the structure-restricted
correlation thesis is a necessary condition of the multiple realizability
of mental properties. So if materialist functionalism is true, then the
structure-restricted correlation thesis follows automatically. But even
if mental properties are not functional properties, nevertheless
the structure-restricted correlation thesis still seems to be true, because
all that it says is that X (i.e., an animal) has a mental property
at a time only if X has a certain physical structure and there is
some lawful connection between instantiations of that mental property and
basic properties of that physical structure, and this seems unexceptionable.
Indeed, it is important to see that the structure-restricted correlation
thesis is perfectly compatible with various denials of materialism, whether
reductive materialism or nonreductive materialism. Even if mental properties
are neither identical with nor in any sense supervenient on physical properties,
there can still be a structure-restricted correlation between mental properties
and physical properties in animals.

How can we isolate a given structure-restricted correlation? The correct
answer, I think, is the one offered by Kim, namely that we isolate it by
finding the causal-functional characterization of that mental property,
and then correlating the causal-functional role picked out by that characterization
with a certain species-specific or sub-species-specific neurobiological
constitution in animals. Again however, it is crucial to remember that
we need not identify mental properties with functional properties
in order to do this: all we need is to have a causal-functional characterization
of the relevant mental property. Consider, for example, the causal-functional
characterization of the mental property of being in pain that I sketched
in section III: pain is the animalís subjective experience of tissue damage
or neurobiological systemic disruption within its own body; pain is subject-dependent,
multiply realizable, and multiply functional; and pain has a necessary
connection (other things being equal) to animal behavior. The causal-functional
role of pain is multiply realized in humans, apes, bats, and so-on, and
therefore determines a set of structure-restricted correlations between
the mental property of being in pain and different species-specific or
sub-species-specific neurobiological constitutions.

This point leads to one last concept that we need before we get to my
argument for the MCP: the concept of a "schematization" of a mental property.
The basic idea behind the schematization of a mental property is that animals
of different species or sub-species will typically subjectively experience
the same sorts of things--e.g., colors, sounds, or pain--somewhat differently,
precisely because their neurobiological constitutions are somewhat different,
and also in some sort of systematic relation to the various differences
in neurobiological constitution. Again, schematization is the way that
different types of animal body directly affect the specific character of
phenomenal consciousness, generally in the form of a distinctive species-specific
body-image that gives a correspondingly distinctive underlying phenomenal
spatiotemporal organization to the animalís sensations and affects. Slightly
more abstractly put, a mental property is schematized just in case the
specific subjective experiential character of its instances is regularly
and systematically modified and shaped (via a body-image) by the multiple
realizations of its corresponding causal-functional role under different
structure-restricted correlations. My thesis is then that necessarily all
phenomenal consciousness is schematized. This is what I will call the
schematization principle. Human pain and bat pain are both pain, in
the sense that they each play the same causal-functional role in the human
species (homo sapiens) and the bat species (michrochiroptera): but in virtue
of the schematization principle it seems very likely that bat pain is sharply
different from human pain, not merely neurobiologically, but also phenomenologically.
Indeed it is precisely schematization, I think, that implicitly drives
the basic intuition that Nagel uses to motivate the mental-mental gap.
We lack any sort of adequate conceptual understanding of what it is like
to be a bat precisely because the subjective experiences of humans and
of bats are schematized very differently, and because the differing contents
of schematization across different species or sub-species are given directly
only to the phenomenally conscious members of those very species or sub-species.

Here now, finally, is my argument for the MCP.

Assume Nagelís conception of phenomenal consciousness as what it is like
to be for an organism, understood now as what it is like to be for an animal.

Phenomenally conscious states like pain have corresponding causal-functional
characterizations that describe their causal-functional roles.

The causal-functional role of pain is multiply realized under different
species-specific or sub-species-specific structure-restricted correlations.

This in turn implies the schematization principle as applied to pain.

Given the schematization principle and Nagelís mental-mental gap, there
is good reason to believe that bat pain is not only phenomenologically
very different from human pain but also in fact conceptually inaccessible
for us.

We have good reason to believe that a subjective experience can be as morally
significant as human pain only if it is phenomenologically quite similar
to human pain. This is because our reason for believing that the subjective
experience of pain in our species is even sometimes morally significant
is necessarily based on first-person evidence. But the less phenomenologically
similar a given subjective experience-type E1 (say, bat
pain) is to another subjective experience type E2 (say,
human pain), then the less reason we have to believe that E1
has all or even any of the consciousness-based properties that E2
has.

So since there is good reason to believe that bat pain is not only phenomenologically
very different from human pain but also in fact conceptually inaccessible
for us, then there is good reason to believe that bat pain is not as morally
significant as human pain.

All and only persons can suffer.

Suffering has fundamental moral significance, because personhood in the
moral sense entails both the right to life and also the right not to suffer.

Now some humans, and also some non-humans, are persons in the moral sense
and therefore can suffer. By contrast, since bats are not persons, bats
are capable of having only bodily pain, and cannot suffer.

Some human or non-human animals are not persons but will in the natural
course of their genetic development become persons. To the extent that
these animals have already begun to acquire some of the psychological sub-capacities
that are jointly constitutive of personhood and the capacity for suffering,
there is good reason to believe that they are more morally significant
than bats, since bats will never become persons or suffer in the natural
course of their genetic development.

Therefore, there is good reason to believe (i) that the pain of human or
non-human animals that are persons is more morally significant than the
pain of bats, and also (ii) that the pain of human or non-human animals
that will become persons in the natural course of their genetic development
is more morally significant than the pain of bats.

This preliminary conclusion is what I will call the bat-restricted
moral comparison principle. It is crucial to see that this principle
could not be restricted to apes. This is because (as evidence from
cognitive ethology strongly indicates) apes are persons, and also because
there is little or no reason to think that the schematization principle
and Nagelís mental-mental gap will entail that the pain of apes is phenomenologically
very different from human pain or conceptually inaccessible to us, in view
of the fact that (as evidence from cognitive neuroscience strongly indicates)
the neurobiological constitution of apes is very similar to that of normal
humans. Indeed, the degree--if not the precise kind--of neurobiological
difference between normal apes and normal humans seems to be not appreciably
larger than the degree of neurobiological difference between many humans
who are victims of Alzheimerís disease, autism, cerebral palsy, Downís
syndrome, or spina bifida, and normal humans.

Now take the bat-restricted moral comparison principle and substitute
for the first occurrence of Ďbatsí the phrase Ďany non-human species of
animals that are non-personsí and substitute for the second occurrence
of Ďbatsí the phrase Ďany non-human species of animals that will never
become persons in the natural course of their genetic developmentí. These
substitutions are justified by the concept of a person in the moral sense,
together with the thesis that all and only persons can suffer, together
with the thesis (shared by Bentham and Singer) that the capacity for suffering
confers fundamental moral significance on an animal. Making those substitutions,
we get

Therefore, there is good reason to believe (i) that the pain of human or
non-human animals that are persons is more morally significant than the
pain of any non-human species of animals that are non-persons, and also
(ii) that the pain of human or non-human animals that will become persons
in the natural course of their genetic development is more morally significant
than the pain of any non-human species of animals that will never become
persons in the natural course of their genetic development.

This intermediate conclusion is what I call the cross-species
moral comparison principle.

Now, finally, take the cross-species moral comparison principle and
substitute for both occurrences of Ďany non-human species of animalsí the
phrase Ďany species of animalsí. These substitutions are justified by anti-speciesism
as applied to humans, or the rejection of the thesis that some species-specific
difference between humans and non-humans is the sole or primary determinant
of the moral significance of animals or moral discriminations between animals.
If by some cosmic accident it turned out that no humans were persons, and
that all persons were non-humans, then the basic rationale for the MCP
would hold just the same. Making those substitutions, we get

Therefore, there is good reason to believe (i) that the pain of human or
non-human animals that are persons is more morally significant than the
pain of any species of animals that are non-persons, and also (ii) that
the pain of human or non-human animals that will become persons in the
natural course of their genetic development is more morally significant
than the pain of any species of animals that will never become persons
in the natural course of their genetic development.

And this last conclusion is the MCP.

VI. Conclusion

The ethical payoffs of the MCP are considerable. If I am right, then
we have good reason to extend serious moral consideration to some non-human
animals and in particular to apes, but no good reason to treat all animals
equally. We also have good reason to think that the arbitrary late-term
abortion or torture of normal human and ape fetuses, the arbitrary infanticide
or torture of normal human and ape infants, the arbitrary killing or torture
of toddlers and normal young apes, the arbitrary killing or torture of
many victims of Alzheimerís disease, autism, Downís syndrome, and spina
bifida, the arbitrary killing or torture of normal adult apes, as well
as the arbitrary killing or torture of K-persons of any species,
are all impermissible. But we have no good reason to think that the abortion
of human fetuses prior to the onset of sentience or phenomenal consciousness,
or the killing of merely and permanently sentient humans or of non-sentient
humans, including anencephalic infants and humans in persistent vegetative
states, are impermissible.

It should be noted however that the MCP does not entail that
human or non-human animals that are non-persons, like bats, are without
any moral significance at all. The capacity for suffering confers fundamental
(or basic-rights-entailing) moral significance on an animal, and the
fact that an animal is not capable of suffering entails that it is less
morally significant than any animals that are capable of suffering: but
this fact does not wholly undermine its moral significance. Animals that
are not persons and are never going to develop into persons, and therefore
are incapable of suffering, do not have intrinsic non-instrumental
moral significance. But they might well have extrinsic or instrumental
moral significance, and possibly of a high degree. For example, it seems
very wrong to torture non-human animals that are merely sentient or phenomenally
conscious (e.g., bats) because such torture strongly tends to promote the
brutal treatment of non-human animals that are or are going to become persons,
just as it seems very wrong to torture human animals that are merely sentient
or phenomenally conscious (e.g., those in the final stages of Alzheimerís
disease, or extreme victims of cerebral palsy or spina bifida) because
this strongly tends to promote the brutal treatment of human animals that
are or are going to become persons. But it does not seem wrong, other things
being equal, painlessly to kill human animals in the final stages of Alzheimerís
disease, or extreme victims of cerebral palsy or spina bifida. And the
same goes for non-human animals that are merely sentient or phenomenally
conscious.

Here, finally, is another interesting consequence of my argument for
the MCP. If animal ethicists want to hold that "pain is pain is pain, wherever
it is experienced," then they must defend a reductive materialism of the
old-fashioned, now generally rejected, "type-physicalism" variety. In other
words, they must reject both the multiple realization thesis and the structure-restricted
correlation thesis, which are accepted by virtually everyone who works
in mainstream contemporary philosophy of mind, whether materialist or non-materialist,
as well as rejecting Nagelís widely-accepted mental-mental gap argument.
But even if animal ethicists do opt for these highly implausible
views in the philosophy of mind, they still cannot help themselves
to the direct inference from animal pain to animal suffering without committing
the Bentham-Singer Fallacy.